US2481630A

US2481630A - Heater control

Info

Publication number: US2481630A
Application number: US633733A
Authority: US
Inventors: Vernon N Tramontini
Original assignee: Stewart Warner Corp
Current assignee: Stewart Warner Corp
Priority date: 1945-12-08
Filing date: 1945-12-08
Publication date: 1949-09-13
Anticipated expiration: 1966-09-13

Description

Sept. 13, 1949,

2 Sheets-Sheet 1 Filed Dec. 8, 1945 Sept. 13, 1949. v@ N. TRAMONTINI 2,481,530

HEATER CONTROL Filed Dec. a, 1945 2 Sheets-Sheet z I I 1 v1,"

J I )6 ill/was Patented 13, 1949 HEATER CONTROL Vernon N. Tramontini, Indianapolis, Ind., assignor to Stewart-Warner Corporation, Chlcago, 111., a corporation of Virginia Application December 8, 1945, Serial No. 533,733

3 Claims;

The present invention relates to heater controls and is, more particularly, concerned with a control system and control device for regulating the heat output of a small combustion heater in ac cordance with demand conditions.

Recently there have been developed combustion type heaters for use in automotive vehicles and for like heating purposes in which a wide range of heat outputs is possible simply by controlling the rate of fuel supply to the heater. One example of such a heater is illustrated and described in the copending application of George Wallen and Vernon N. Tramontini, filed June 14, 1946, which has been given Serial No. 676,776. A typical heater of this type, for example, may have a high heat output of approximately 20,000 to 25,000 B. t. u. per hour and a low heat output under reduced fuel supply conditions of something on the order of 4,000 B. t. u. per hour. Under normal conditions, 4,000 B. t. u. per hour is not sufficient to keep the occupants of an automobile warm excepting in extremely mild weather. On the other hand, 20,000 B. t. u. per hour is far too much for continuous operation, but such high output is an advantage in that it permits the automobile to be quickly heated to a comfortable temperature even in severe weather.

The principal object of the present invention is to provide an improved control system and controller for such a heater which will modulate the heat output according to the requirements of the occupants in such manner that the temperature of the ventilating air entering the occupied space of the vehicle will be high when the occupied space is quite cold and will taper off as the temperature rises within the occupied space and then will maintain a comparatively constant temperature level thereafter without sharp on-oif cycles.

An additional object of the present invention is to'provide a novel heater control system and controller which avoids abrupt fluctuations in the temperature of the air within the occupied space. Yet another object of the present invention is to provide a novel control system and controller which regulates the heater output so as to obtain a desired temperature for the ventilating air under all conditions and which avoids abrupt fluctuations of the ventilating air temperature.

Still another object of the present invention is to provide a controller and control system for accomplishing the above at comparatively low cost. a

other objects and advantages will become epparent from the following description of a preferred embodiment of my invention which is illustrated in the accompanying drawings.

In the drawings in which similar characters of reference refer to similar parts throughout the several views:

Fig. 1 is a diagrammatic illustration of an automobile partly in longitudinal section showing the layout of a typical heating system and one arrangement of the controller and control system comprising the present invention associated therewith;

Fig. 2 is a longitudinal vertical sectional view through a controller which incorporates the present invention. Fig. 2 has been taken with one half of the controller case removed and therefore only a portion of the structure is illustrated in section;

Fig. 3 is a transverse vertical sectional view which may be considered as taken in the direction of the arrows along the line 3-3 of Fig. 2;

Fig. 4 is a similar sectional view which may be considered as taken in the direction of the arrows along the line 4-4 of Fig. 2;

Fig. 5 is an end view of the device;

Fig. 6 is a bottom view; and

Fig. 7 is a diagrammatic representation of an electrical circuit suitable for use with the device .of the present invention.

The automobile I0 is provided with a driver's compartment l2 separated from the engine compartment It by a dash l6. Within the engine compartment, the heater i8 is located in a position above the engine 20 and is provided with a blower 22 on its inlet side. The inlet of the blower is connected by means of a duct 24 to a ram or air inlet opening 26 located behind the radiator grill in a position above the radiator 28.

The air outlet end of the heater is connected to a ventilating air duct 30 which extends rearwardly and downwardly to a longitudinally extending duct 32 arranged beneath the floor 34 of the vehicle. This duct is provided with

outlets

36 and 38 located respectively beneath the drivers seat 40 and the rear seat 42. A fuel line 44 is connected to the heater in such manner that the fuel under pressure passes through an on-andoff solenoid valve 46 and thence through a rerestricting solenoid valve 48 before arriving at the heater. These valves are so constructed that when the valve 46 is de-energized, it is in closed position and no fuel is permitted to flow therethrough, while when this valve is energized, fuel in adequate quantity to operate the heater at the high heat output level is permitted to flow.

Valve 48 is so constructed that when deenergized and therefore closed it leaks a sumcient quantity of fuel to operate the heater at the low heat output level. When this valve is energized, it opens and ofiers substantially no restriction to the flow of fuel therethrough. It is apparent, therefore, that so long as the valve 46 is deenergized, the heater will not operate. When both valves are energized, the heater will operate at its high output and when valve 46 is energized and valve 48 de-energiz'ed, the heater will operate at the low heat output rate. 1

Referring to Fig. '7, it will be seen that the automobile battery 58 supplies electric power through the heater on-and-ofl switch 52 to three thermostatic switches, 54, 56 and 58, and the motor 53 for the blower 22. Of these switches, switch 54 is connected to the hot wire igniter 68 of the heater I8, the other end of the igniter being grounded. Thermostatic switch 56 is connected to one terminal of the on-and-oif solenoid valve 46, the other terminal of this valve being grounded, while the thermostatic switch 58 is similarly connected to the restricting solenoid valve 48. In order to prevent sparking at the contacts of the thermostatic switch '58, this switch is provided with a capacitor 62.

The

switches

54 and 56 are arranged closely adjacent the heater at the hot air outlet end so that these switches will be sensitive to the temperature of the air leaving the heater.

When switch-'52 is closed, if the heater has not been operating recently, the

switches

54 and 56 will be closed, and thus the igniter 60 is energized and quickly comes up to ignition temperature. Also the solenoid valve 46 will be opened, thereby permitting fuel to flow to the heater. Soon after combustion is well established, the temperature of the outlet air from the heater will rise sufficiently to open the switch 54 and de-energize the igniter 68. The purpose of the switch 56 is to serve as an overheat safety control so as to shut off the fuel supply completely if the temperature of the air leaving the heater becomes excessively hot as might occur if the blower 22 fails to operate. The switch 58 operates as will be described presently to cycle the heater between the high heat output position and the low heat output position as. required to maintain a comfortable temperature within the automobile. The present invention is concerned primarily with the construction and operation of the switch 58.

The switch 58 is comprised of a case 64 which in the present embodiment is shown as being formed in halves which are molded from a suitable plastic material, such as Bakelite," for instance. As shown, the molded case includes a lower closed compartment 66, an L-shaped air passage 68 through the device, an upper closed small compartment I8 and a second air passage I2 which intersects the passage 68.' In general, the case is shaped to provide an inlet fitting I4 which is connected to a tube I6 preferably of low thermal conductivity material which extends from the drivers compartment I2 through the dashboard I6 and into the duct 38. I Preferably the tube I6 should extend within the duct 38 in a direction toward the heater and into a position comparatively close to the heater for reasons which will appear presently. .Also, to prevent heat loss and to obtain better control, the duct 38 preferably should be formed of a material of low thermal conductivity or else should be insulated with asbestos or glass wool.

' vided with a Venturi throat 88 to increase the velocity of the air just before it leaves the controller. The flow of air through the passage 68 is produced both by the pressure built up in the duct 38 by the blower 22 and by the dynamic effect of the air flowingthrough the duct 38 and impinging against the mouth of the tube 38. It is apparent, therefore, that if the outlets beneath the seats are closed or partially closed, the flow rate through the duct 88 will be reduced, but the static pressure will rise, with the result that the flow rate through the tube 16 will remain approximately the same. Conversely, if the outlets are wide open and the pressure drop through the duct system is therefore low, the

static pressure within the duct 38 will be low,

but since the velocity will be high, the dynamic pressure at the inlet of the tube I6 will be high, thereby insuring suflicient flow through'the controller 58.

I prefer that the tube I6 be of low heat loss material and have its inlet end comparatively close to the heater, since otherwise closing the outlet openings beneath the seats would reduce the flow rate through the duct 38 to such a low point that heat loss from the large duct 30 might cool the duct air appreciably before it reached the tube 16. Therefore, if the tube I6 does not extend well into the duct 38, the temperature of the air picked up by the tube 16 and delivered to the controller 58 may be considerably cooler than the temperature of the air leaving the heater.

The branch passage I2 is comprised of a generally rectangular chamber 82 open at the bottom of the device, this opening being covered by a grill 84 and by an outlet connection 86 which leads from the chamber 84 to the throat of the venturi 88. Air flowing through the tube 16 and passage 68, therefore, produces a low pressure area at the Venturi throat 88 which serves to aspirate air from the outlet connection 86 with the result that air is drawn in through the grill 84, passes through the chamber 82, and joins the air stream passing through the venturi 88, the mixture leaving the device at the opening I8.

Inasmuch as the controller is mounted within the drivers compartment as, shown in Fig. 1, the air drawn through the chamber 82 will be at the temperature prevailing within the drivers compartment, while the air passing through the passage 68 will be at approximately the temperature prevailing at the heater outlet.

A thermostatic bimetal strip 88 is secured at one end by means of screws 88 passing through the partition 98 which separates the passage 68 from the compartment 66, so that it is located within the passage '68 and is therefore subject to the temperature of the air flowing therenected to a pin 94 which extends downwardly through an opening 96 in the partition 88. At

its'lower end, the pin 84 is similarly connected to a light spring strip I08 at its free end, the opposite end of the strip I00 being secured by the same screws 98 which attach the bimetal strip 88. The purpose of strip I00 is to keep the pin 94 in alignment as the bimetal strip 88 moves up and down. The extreme lower end of the pin 94 is provided with a contact button I82 which is positioned just below the free end of the strip I88. This contact button rests against the upper surface of an arcuate cam I84, the profile of which is shown in Fig. 4. This cam is connected by means of a spoke I08 with a hub I08 of insulating material, such as hard fiber, for instance, and a counterbalance II 0 arranged on the opposite. side of the hub. The hub I08 is secured to a shaft H2 which is journaled to rotate in bearings located at opposite ends of the chamber 68, the cam I04 being restrained against longitudinal movement by tubular insulating spacers 4 which surround the shaft H2.

One end of the shaft II2 extends through and into the chamber 02 and is secured to one end of a coiled bimetal strip II 8 which extends longitudinally of the device, the other end of the bimetal being secured to a stub shaft II8 journaled for rotation in the wall at the front end of the device and provided with a gear I20 located Just inside the compartment 82. The gear I20 is meshed with a worm I22 driven by a flexible shaft I24 of the speedometer drive type, the opposite end of the flexible shaft I24 being connected to a control knob I26 located upon the automobile dash within convenient reach of an operator.

Preferably the contact point I02 is made of silver or other good electrical contact material, and at least the rim surface of the cam I04 is silver plated. The cam I04 is connected by means of a flexible pigtail lead I28 with a terminal I30 located at the top of the device. Similarly, one of the screws 80 in contact with the bimetal strip 88 and the spring strip I 00 and hence in contact with the button I02, is connected by a lead I32 with a second terminal binding post I 34 also located at the top of the device. The capacitor 82 previously referred to is located within the compartment and is connected across the terminal I30 and I34 so as to be across the contacts I02 and I04.

The device operates in the following manner. If it is assumed that the automobile has remained out of doors in cold weather until-the temperature within the compartment is well below the comfort level, the thermostatic switch 88 will be cooled and will tend to urge the contact point I 02 downwardly. Also the coiled bimetal element II6 will be chilled, thereby causing it to rotate the cam I04 to the position shown in full line in Fig. 4. In other words, it rotates this cam such that the higher portion of the cam surface is against the contact button I02. When the heater is started under these conditions in the manner previously described, the restricting solenoid valve 46 will be energized, thereby permitting a full flow of fuel to the heater so as to give the high heat output for which the heater is designed, as for example, 20,000 B. t. u. per hour. The temperature of the air passing through the duct 30, therefore will soon become quite high with the result that the temperature of the air passing through the tube 16 and through the passage 68 in the controller will also be high.

This hot air heats the bimetal element 88 to approximately the ambient temperature in the passage 88, and this causes the free end '02 to tend to move upwardly. However, inasmuch as the strip 88 is already bent upwardly because of the high position of the cam I04, the contacts I02 and I04 will not separate. In other words, heating the bimetal element 88 under these c0nditions merely tends to relieve the spring action of the bimetal element to some extent.

The hot air passing through the passage 88 draws air inwardly through the grill 82 in the manner previously described, so that the bimetal element II 8 remains cold even though the bimetal element 00 may be quite hot. The bimetal element II8 therefore keeps the cam in the position shown in full line in Figs. 4, so long as the temperature of the air within the automobile compartment is below a comfortable level. The heater therefore continues to operate at its high output rate until the automobile body temperature comes up to a point slightly below the comfort level. At this point, air aspirated through the grill 84 has raised the temperature of the bimetal element I I6 sufl'lciently to cause it to unwind somewhat so as to move the cam I04 toward the position shown in broken lines in Fig. 4. This separates the contact I02 from the arcuate surface of the cam I04 and permits the solenoid valve 48 to close so as to reduce the rate of fuel supply to the heater and to shift the heater to its low heat output position. This is done just before the temperature in the compartment reaches a comfortable level, in order to prevent the temperature from overshooting. As the temperature within the duct 30 decreases, the temperature of the air within the passage 88 similarly decreases, thereby cooling the thermostatic strip 88 and permitting it to move downwardly somewhat. The result is that after a short interval of low heat operation, the contact point I02 is again brought against the contact strip of the cam I04 so as to energize the restricting solenoid valve 48, thereby causing an increase in the temperature of air passing through the duct 30 and passage 68 which again heats the bimetal strip 88 and separates the contacts I02 and I04.

If the temperature within the occupied compartment continues to rise, the cam I04 will be rotated more and more toward the dotted line position shown in Fig. 4, which in turn reduces the ratio of high heat output time to low heat output time. It is apparent, therefore, that the mean average temperature of the air flowing into the automobile compartment is higher when the temperature within the compartment is low, that is, with the cam more toward the position shown in full line in Fig. 4, than when the temperature therein is comparatively high, that is, more toward the position shown in broken lines in Fig. 4.

If the temperature within the drivers compartment after it reaches equilibrium, is higher or lower than the occupants desire it, this can be corrected by rotation of the knob I26 which shifts the starting position of the bimetal coil I I6.

In order to maintain the temperature within the automobile body substantially constant without too great periodic fluctuations, it is desirable that the temperature of the bimetal coil II8 have more efi'ect upon the restricting solenoid valve circuit than the temperatureof the air in the duct 30. I have found a good compromise to be one such that approximately one degree of temperature variation of the element II8 will have approximately the same efiect upon the contacts I02 and I04 as ten degrees of temperature variation of the bimetal strip 88. In other words, ten degrees of variation in the temperature of bimetal strip 88 should produce approximately the same amount of motion of the contact I02 vertically as one degree change in temperature of the coil II8 will produce in the vertical component of movement produced by rotational movement of the cam I04.

From the above description of a preferred em- I bodiment of my invention, it is apparent that the heat output. or, in other words, the mean average temperature of the air in the duct 30, will decrease as the temperature within the car body rises toward a comfortable level so as to prevent overshooting, and that similarly thetemperature of the air will decrease gradually if for some reason the compartment has been heated to too high a temperature and-it is desired to reduce this temperature.

Having described my invention, what I claim as new and useful, and desire to secure by Letters Patent of the United States, is:

1. A device of the type described for controlling the heat output of a heater, said heater having a hot air outlet duct comprising means forming an air passage, said passage being adapted to be connected on its inlet side with said hot air duct, another portion of said passage being formed to provide a Venturi throat, first thermostatic means in said passage responsiveto the temperature -of the air flowing therethrough, means forming a second air passage, said second air passage having an inlet openingadapted to receive air from the space to be heated and an outlet opening at said Venturi throat, second thermostatic means in said second passage responsive to the temperature of the air flowing therethrough, a first contact and a second contact co-operating therewith, said first contact being connected to be moved away from said second contact by said first thermostatic means upon an increase in the temperature of said first thermostatic means and said second contact being connected to be moved away from said first contact by said second thermostatic means upon an increase in the temperature of said second thermostatic means.

2. A heater system for an automotive vehicle or the like comprising means forming a combustion chamber, a heat exchanger to receive hot products of combustion therefrom and through which ventilating air is adapted to be passed in heat exchange relation thereto, means for supplying fuel to said combustion chamber, said supplying means including a magnetic valve which in one position permits suflicient fuel to flow to operate the heater at a high output level and in another position restricts the flow of fuel to the burner so as to operate the heater at a lower output level, a bimetallic blade responsive to the temperature of the ventilating air leaving the heater, a pair of'switch contacts, one of said contacts being operated by said bimetallic blade, circuit means including said contacts and said valve for cycling said fuel supply system from the high to the low position and back to the high position rapidly accordingly as'the temperature of the ventilating air leaving the heater increases and then decreases, a second bimetallic element responsive to the temperature of the space to be heated, said second bimetallic element being connected for moving the second of said switch contacts toward and away from the first contact as the temperature within the space to be heated falls or rises above a predetermined level so as to determine the duct tempera-' ture at which'said switch is opened or closed by high output level and in another position restricts the flow of fuel to the burner so as to operate the heater at a lower output level, a thermostatic element responsive to the temperature of the ventilating air leaving the heater, a pair of switch contacts, one of said contacts being operated by said thermostatic element, circuit means'including said contacts and said electrically operated flow controllerfor cycling said fuel supply system from the high to the low position and back to the high position rapidly accordingly as the temperature of the ventilating air leaving the heater increases and then decreases, a second thermostatic element responsive to the temperature of the space to be heated, said second thermostatic element being connected for moving the second of said switch contacts toward and away from the first contact as the temperature within the space to be heated falls or rises above a predetermined level so as to determine the duct temperature at which said switch is opened or closed by the first said thermostatic element.

' VERNON N. TRAMONTINI.

, a REFERENCE S crrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 922,783 Korting May 25, 1909 2,164,882 Miles July 4, 1939 2,259,061 Gamer Oct. 14, 1941 2,262,496 Hobbs Nov. 11, 1941 FOREIGN PATENTS Number Country Date 318.699 Great Britain Sept, 12, 1929